1. Field of the Invention
The present invention relates to a system and method for sensing air velocity without requiring external power supply; in particular, a system and method for sensing air velocity without requiring external power supply, aiming to simplify the condition inspection of the ventilation system.
2. Description of the Related Art
In an effort to ensure air quality in the working area, most companies or factories would install ventilation or exhaust systems. However, given the accessibility of the ventilation or exhaust systems, only few of them would further install monitoring systems to oversee the working condition of the ventilation system. Usually, companies or factories would use anemometers or smoke tubes to verify the efficacy of the ventilation system. However, due to many nagging problems involved in the existing checking procedure, many companies or factories have lacked the incentive to perform the efficacy check of the ventilation or exhaust systems in a way that matches up standard procedures.
To keep their employees in good health and to meet the demand of unique manufacturing process, almost all companies or factories would set up ventilation or exhaust systems to keep air moving, so that the employees would not have difficulty breathing. In addition to basic specifications set out for the installation of the ventilation system, laws and regulations also require that ventilation systems in certain workplaces be kept under specific working conditions, in terms of their minimum air exchange rate, minimum air velocity, and minimum negative pressure, etc. Even so, however, conventional factories still do not put these requirements into effective practice. What's more, frequent clogging and leaking in the air ducts also pose concerns for the ventilation systems. As a result, not only do ventilation systems have to be subject to immediate function tests upon installation, but, during the life cycle of the running system, condition inspections also have to be conducted on a regular basis. Some factories in the high-tech industry even put the ventilation system under round-the-clock monitoring. Most companies or factories opt for a regular fix-frequency monitoring method, as shown in FIG. 6 and FIG. 7. FIG. 6 shows a schematic view, where air velocity is measured in the air duct. To take the measurement, one has to rely on a climbing device such as a ladder or a box to be elevated to the extent that a Pitot tube can be inserted into an air duct 62 to take both the velocity pressure and the static pressure before these measurements are converted into an air velocity value to be shown on a display 63 for reading. Despite its potential to get more accurate data, this method remains taxing in terms of its accessibility.
FIG. 7 shows a schematic view, where a smoke tube is used to test the airflow in a fume hood. To begin with, the tester uses a smoke tube 71 to spray power into the fume hood 72. Interactions between the powder and the air would result in smog 73, whose dispersion direction would give the tester a rough idea about the airflow and the air velocity. However, the accuracy of this method is riding on the experience of the tester. For many of the factories, either method is demanding and requires professionalism. Therefore, only few of them would, in effect, perform condition inspection of the ventilation systems on a regular basis. Improving the testing methods and the operating procedures involved would provide the solution to the problem.
In a word, the disadvantages of the conventional condition inspections of the ventilation system can be specified as follows: (1) the tester has to climb up and down a climbing device to take the measurement, which is taxing and needs improving in terms of accessibility; (2) the adjustment of the instruments involved and the way the measurement is performed require professionalism, a lot of which has to rely on the experience of the tester.
To overcome these problems, it is desirable to develop an air velocity sensing system not requiring external power supply, in an attempt to make easy the condition inspection of the ventilation system.